Force-velocity profile: imbalance determination and effect on lower limb ballistic performance

Using a simple model to systematically examine the influence of force-velocity profile and power on vertical jump performance with different constraints

Power, and recently force-velocity (F-V) profiling, are well-researched and oft cited critical components for sports performance but both are still debated; some would say misused. A neat, applied formulation of power and linear F-V in the literature is practically useful but there is a dearth of fundamental explanations of how power and F-V interact with human and environmental constraints. To systematically explore the interactions of a linear F-V profile, peak power, gravity, mass, range of motion (ROM), and initial activation conditions, a forward dynamics point mass model of vertical jumping was parameterised from an athlete. With no constraints and for a given peak power, F-V favouring higher velocity performed better, but were impacted more under real-world conditions of gravity and finite ROM meaning the better F-V was dependent on constraints. Increasing peak power invariably increased jump height but improvement was dependent on the initial F-V and if it was altered by changing maximal force or velocity. When mass was changed along with power and F-V there was a non-linear interaction and jump improvement could be almost as large for a F-V change as an increase in power. An ideal F-V profile cannot be identified without knowledge of mass and ROM.

Validity and Reliability of the Acceleration-Speed Profile for Assessing Running Kinematics' Variables Derived From the Force-Velocity Profile in Professional Soccer Players

ABSTRACT

Alonso-Callejo, A, García-Unanue, J, Guitart-Trench, M, Majano, C, Gallardo, L, and Felipe, J. Validity and reliability of the acceleration-speed profile for assessing running kinematics' variables derived from the force-velocity profile in professional soccer players. J Strength Cond Res 38(3): 563-570, 2024-The aim of this research is to assess the validity and reliability of the acceleration-speed profile (ASP) for measuring the mechanical variables of running kinematics when compared with the force-velocity profile (FVP) obtained by reference systems. The ASP and FVP of 14 male players of an elite football club were assessed during a competitive microcycle. Three ASPs were tested according to the number and type of sessions included in its plotting (ASP1: 5 training sessions and competitive match; ASP2: 5 training sessions; ASP3: competitive match). Force-velocity profile was tested 4 days before match (MD-4) with a 30-m linear sprint using 3 previously validated devices (encoder, mobile App, and global positioning system). Level of significance was p < 0.05. Acceptable reliability (intraclass correlation coefficient > 0.5) was found between the ASP1 and the encoder for all variables (F 0 -A 0 , V 0 -S 0 , and V max ). The more reliable ASP method was the ASP1 showing a lower bias than the ASP2 and ASP3 methods for almost all variables and reference systems. For ASP1, lower mean absolute error (MAE: 0.3-0.5) and higher correlation (P-M corr: 0.57-0.92) were found on variables related to the velocity in comparison with variables related to the early acceleration phase (F 0 -A 0 ; MAE: 0.49-0.63; P-M corr: 0.13-0.41). Acceleration-speed profile, when computed with data from a complete competitive week, is a reliable method for analyzing variables derived from velocity and acceleration kinematics. From these results, practitioners could implement ASP and the applications of the FVP previously studied, such as resistance training prescription, performance assessment, and return-to-play management.

Effect of individualised strength and plyometric training on the physical performance of basketball players

The aims of this study were to examine the effects of eight weeks of individualised force-velocity imbalance (F-Vimb) training on physical performance in basketball players and to analyse the differences in physical performance between two periods of time (four to eight weeks) with this training. Thirty male players (age, 22.8 ± 5.68 years; height, 1.87 ± 0.07 m; body mass, 86.3 ± 11.1 kg) were divided into an intervention group (INT, n = 15), who performed an individualised training based on individual F-Vimb; and a control group (CON, n = 15), who underwent a non-individualised training programme; both groups performed two days/week of intervention and the same pre-season basketball training. At baseline, at four weeks, and at eight weeks of intervention, an assessment was performed including countermovement-jumps, unilateral drop jumps, triple hop test, force-velocity profile, sprint and change of direction (COD). At four weeks, the INT showed improvements in sprint and vertical jumping actions (≥3.76%, ES ≥0.44, p ≤ 0.02). At eight weeks, the INT continued to improve vertical jumping actions (p < 0.05) and showed improvements in horizontal jumping (6.80%, ES = 0.45, p < 0.01) and COD (≥2.99%, ES ≥0.96, p < 0.01). A significant reduction in F-Vimb was observed for INT (ES = 0.77, p = 0.01). In contrast, none of these changes were observed in CON. Thus, an individualised F-Vimb training intervention improved physical performance after eight weeks, with changes in sprint and vertical jump after first four weeks. Basketball coaches should optimise the force-velocity profile and improve the performance in sport-related actions as jumping and changing direction.

Jump and sprint force velocity profile of young soccer players differ according to playing position

Our study aimed to compare explosive performance and underlying mechanical determinants explored through F-V profiles in jumping and sprinting among young soccer players based on their playing position. Ninety elite soccer players were categorized into the following positions: goalkeepers, central defenders, wide defenders, central midfielders, wide midfielders, and forwards. Two testing sessions were conducted to measure the 30-metre sprint time (T30) using an over-ground sprint test and jump height (Hmax) through the SJ test. Results demonstrated performance variations among positions. In sprinting, forwards showed greater T30 (4.5 ± 0.14 s) compared to other positions, with goalkeepers exhibiting the lowest T30 (4.86 ± 0.18 s). Forwards also displayed higher maximal theoretical velocity (8.8 ± 0.4 m.s-1) and power output (Pmax) (19.4 ± 2.6 W.kg-1) than other positions, while goalkeepers had the lowest Pmax (16.5 ± 2 W.kg-1). In jumping, forwards (33.2 ± 3.9 cm) and wide-midfielders (33.6 ± 3.8 cm) achieved higher Hmax compared to goalkeepers (29.2 ± 5 cm) and central-midfielders (29.2 ± 3.8 cm). Wide-midfielders (28.5 ± 4.8 W.kg-1) and forwards (27.1 ± 4.3 W.kg-1) surpassed goalkeepers (23 ± 2.8 W.kg-1) and central-midfielders (25.1 ± 3.8 W.kg-1) in Pmax. Our findings reveal substantial position-related disparities in F-V profiles among elite young soccer players, in sprinting and jumping emphasizing the need for position-specific training programmes to optimize player development and on-field performance from an early age.

Agreement in Squat Jump Force-Time Characteristics Between Smith Machine and Free-Weight Squat Jump Force-Time Characteristics

ABSTRACT

Kotani, Y, Lake, J, Guppy, SN, Poon, W, Nosaka, K, and Haff, GG. Agreement in squat jump force-time characteristics between Smith machine and free-weight squat jump force-time characteristics. J Strength Cond Res 37(10): 1955-1962, 2023-The purpose of this study was to determine whether squat jump (SJ) force-velocity (FV) and load-velocity (LV) profiles created using free-weights agree with profiles created with a Smith machine. Fifteen resistance-trained male subjects (age = 26.4 ± 2.5 years; height = 1.75 ± 0.09 m; body mass = 82.6 ± 13.4 kg) participated in this study. All subjects completed 2 familiarization and 2 experimental sessions using both the Smith machine and free-weight SJs each separated by 48 hours. During the experimental trials, progressively loaded SJs were performed in a quasi-randomized block order with loads between 21 kg and 100% of the subject's body mass. Agreement between exercise mode was determined with a weighted least products regression analysis. No fixed or proportional bias was noted between exercise modes when using peak velocity (PV) and mean velocity (MV) to create an FV profile. There was no fixed and proportional bias present for the LV profile when the profile was created with PV. When the LV profile was calculated from MV, fixed and proportional bias were present, indicating that MVs were significantly different between exercise modes. In addition, the free-weight FV and LV profiles exhibited poor to good relative and good to poor absolute reliability. Furthermore, when created using the Smith machine, both profiles exhibited poor to moderate relative and absolute reliability. Based on these data, caution should be used when interpreting LV and FV profiles created with these 2 methods.

The 2-Point Method: Theoretical Basis, Methodological Considerations, Experimental Support, and Its Application Under Field Conditions

The "2-point method," originally referred to as the "2-load method," was proposed in 2016 by Prof Slobodan Jaric to characterize the maximal mechanical capacities of the muscles to produce force, velocity, and power. Two years later, in 2018, Prof Jaric and I summarized in a review article the scientific evidence showing that the 2-point method, compared with the multiple-point method, is capable of providing the outcomes of the force-velocity (F-V) and load-velocity (L-V) relationships with similar reliability and high concurrent validity. However, a major gap of our review was that, until 2018, the feasibility of the 2-point method had only been explored through testing procedures based on multiple (more than 2) loads. This is problematic because (1) it has misled users into thinking that implementing the 2-point method inevitably requires testing more than 2 conditions and (2) obtaining the data from the same test could have artificially inflated the concurrent validity of the 2-point method. To overcome these limitations, subsequent studies have implemented in separate sessions the 2-point method under field conditions (only 2 different loads applied in the testing protocol) and the standard multiple-point method. These studies consistently demonstrate that while the outcomes of the 2-point method exhibit comparable reliability, they tend to have slightly higher magnitudes compared with the standard multiple-point method. This review article emphasizes the practical aspects that should be considered when applying the 2-point method under field conditions to obtain the main outcomes of the F-V and L-V relationships.

Assessing climbers' pull-up capabilities by differentiating the parameters involved in power production

This study explored the capabilities of sport climbers to pull up with arms. The methodology aimed at assessing (i) concentric capabilities of arm muscles, (ii) body coordination skills (iii) characteristics of energy storage and (iv) capabilities to resist fatigue. Twenty-eight climbers were tested and the force exerted was recorded during three pull-up exercises: jump tests (with or without coordination, or preceded by an eccentric phase), incrementally weighted pull-ups and maximum number of pull-ups. Force, velocity, muscle power and muscle work were analysed using ANOVA with post-hoc tests and principal component analysis. Correlations with climbing level were also studied. Overall, jump test results showed that body coordination and stretch-shortening cycle phenomena contributed significantly to performance but only the body coordination was related to the climber's grade level. Muscle work and maximum number of pull-ups are correlated with climbing level which showed that the capacity to resist fatigue is another crucial capability of climbers arms. The development of force capacities appeared crucial for performing whereas the velocity capabilities seemed to originate from the climber's own characteristics/style without correlating with climbing performance. Our study provides the basis for evaluating these parameters in order to help trainers in the diagnosis process and training follow-up.

Enhancing the Initial Acceleration Performance of Elite Rugby Backs. Part I: Determining Individual Technical Needs

PURPOSE

This study sought to quantify the within-individual relationships between spatiotemporal variables and initial acceleration sprint performance in elite rugby backs and to establish a normative data set of relevant strength-based measures.

METHODS

First, the spatiotemporal variables, ratios of step length to step rate and of contact time to flight time, and initial acceleration performance were obtained from 35 elite male rugby backs (mean [SD] age 25 [3] y) over the first 4 steps of 3 sprints. Angular and linear kinematic aspects of technique and strength-based qualities were collected from 25 of these participants. Second, the same spatiotemporal variables were collected from 19 of the participants on 3 further occasions (12 trials in total) to determine the within-individual associations of these variables and initial acceleration performance.

RESULTS

Moderate to very large meaningful within-individual relationships (|r| = .43-.88) were found between spatiotemporal variables and initial acceleration performance in 17 of the 19 participants. From these relationships, a theoretically "desirable" change in whole-body kinematic strategy was individually determined for each participant, and normative strength-based measures to contextualize these were established.

CONCLUSIONS

Meaningful within-individual relationships are evident between sprint spatiotemporal variables and initial acceleration performance in elite rugby backs. Individualized approaches are therefore necessary to understand how aspects of technique relate to initial acceleration performance. This study provides an objective, evidence-based approach for applied practitioners to identify the initial acceleration technical needs of individual rugby backs.

Ecological and Specific Evidence-Based Safe Return To Play After Anterior Cruciate Ligament Reconstruction In Soccer Players: A New International Paradigm

Existing return to play (RTP) assessments have not demonstrated the ability to decrease risk of subsequent anterior cruciate ligament (ACL) injury after reconstruction (ACLR). RTP criteria are standardized and do not simulate the physical and cognitive activity required by the practice of sport. Most RTP criteria do not include an ecological approach. There are scientific algorithms as the "5 factor maximum model" that can identify risk profiles and help reduce the risk of a second anterior cruciate ligament injury. Nevertheless, these algorithms remain too standardized and do not include the situations experienced in games by soccer players. This is why it is important to integrate ecological situations specific to the environment of soccer players in order to evaluate players under conditions closest to their sporting activity, especially with high cognitive load. One should identify high risk players under two conditions: Clinical analyses commonly include assessments such as isokinetic testing, functional tests (hop tests, vertical force-velocity, profile), running, clinical assessments (range of motion and graft laxity), proprioception and balance (Star Excursion Balance Test modified, Y-Balance, stabilometry) and psychological parameters (kinesophobia, quality of life and fear of re-injury). Field testing usually includes game simulation, evaluation under dual-task conditions, fatigue and workload analysis, deceleration, timed-agility-test and horizontal force-velocity profiles. Although it seems important to evaluate strength, psychological variables and aerobic and anaerobic capacities, evaluation of neuromotor control in standard and ecological situations may be helpful for reducing the risk of injury after ACLR. This proposal for RTP testing after ACLR is supported by the scientific literature and attempts to approximate the physical and cognitive loads during a soccer match. Future scientific investigation will be required to demonstrate the validity of this approach.

Level of Evidence

5.

Kinetic and Kinematic Assessment of the Band-Assisted Countermovement Jump

ABSTRACT

Fernandes, JFT, Arede, J, Clarke, H, Garcia-Ramos, A, Perez-Castilla, A, Norris, JP, Wilkins, CA, and Dingley, AF. Kinetic and kinematic assessment of the band-assisted countermovement jump. J Strength Cond Res XX(X): 000-000, 2022-This study sought to elucidate kinetic and kinematic differences between unloaded and band-assisted countermovement jumps (CMJs). In a randomized order, 20 healthy subjects (mass 84.5 ± 18.6 kg) completed 3 repetitions of CMJs across 3 conditions: unloaded (at body mass), low, and moderate band (8.4 ± 1.9 and 13.3 ± 3.3 kg body weight reduction, respectively). For all repetitions, a force platform and linear position transducer were used to record and calculate kinetic and kinematic data. Body weight was significantly different between the unloaded, low, and moderate band conditions (p < 0.05). Peak velocity, absolute peak, and mean force and movement duration displayed a trend that was mostly related to the condition (i.e., unloaded > low > moderate) (p < 0.05). The opposing trend (i.e., moderate > low > unloaded) was generally observed for relative peak and mean force, reactive strength index modified, and flight time (p < 0.05). No differences were observed for mean velocity, movement duration, and absolute and relative landing forces (p > 0.05). The use of band assistance during CMJs can alter force, time, and velocity variables. Practitioners should be aware of the potential positive and negative effects of band assistance during CMJs.

Force-velocity relationship in Paralympic powerlifting: two or multiple-point methods to determine a maximum repetition

Background

Due to the absence of evidence in the literature on Paralympic Powerlifting the present study investigated various methods to assess bench press maximum repetition and the way each method influences the measurement of minimum velocity limit (MVT), load at zero velocity (LD0), and force–velocity (FV).

Objective

To evaluate the precision of the multi-point method using proximal loads (40, 50, 60, 70, 80, and 90% of one repetition maximum; 1RM) compared to the four-point method (50, 60, 70, and 80% of 1RM) and the two-point method using distant loads (40 and 80% and 50 and 80% of 1RM) in in the MVT, LD0, and FV, in bench press performed by Paralympic Powerlifters (PP).

Methods

To accomplish this, 15 male elite PP athletes participated in the study (age: 27.7 ± 5.7 years; BM: 74.0 ± 19.5 kg). All participants performed an adapted bench press test (free weight) with 6 loads (40, 50, 60, 70, 80, and 90% 1RM), 4 loads (50, 60, 70, and 80% 1RM), and 2 loads (40–80% and 50–80% 1RM). The 1RM predictions were made by MVT, LD0, and FV.

Results

The main results indicated that the multiple (4 and 6) pointsmethod provides good results in the MVT (R² = 0.482), the LD0 (R² = 0.614), and the FV (R² = 0.508). The two-point method (50–80%) showed a higher mean in MVT [1268.2 ± 502.0 N; ICC95% 0.76 (0.31–0.92)], in LD0 [1504.1 ± 597.3 N; 0.63 (0.17–0.86)], and in FV [1479.2 ± 636.0 N; 0.60 (0.10–0.86)].

Conclusion

The multiple-point method (4 and 6 points) and the two-point method (40–80%) using the MVT, LD0, and FV all showed a good ability to predict bench press 1RM in PP.

Differences in Force-Velocity Profiles During Countermovement Jump and Flywheel Squats and Associations With a Different Change of Direction Tests in Elite Karatekas

The force-velocity (F-v) relationship has been proposed as a biomechanical characteristic to comprehensively evaluate neuromuscular capabilities within different tasks such as vertical jumping, sprinting and bench pressing. F-v relationship during flywheel (FW) squats was already validated, however, it was never compared to F-v profile of vertical jumps or associated with change of direction (CoD) performance. The aims of our study were (1) to compare F-v profiles measured during counter movement jumps (CMJs) and FW squats, (2) to determine correlations of F-v mechanical capacities with different CoD tests, (3) to investigate the portion of explained variance in CoD tests with the F-v outcome measures. A cross-sectional study was conducted on 39 elite karatekas. They performed CMJs and FW squats using progressive loads to calculate F-v profile outcome variables and different CoD tests (CoD at 90°, CoD at 180°, t-test, short karate specific test (KST) and long KST). Our results showed significantly higher values in all F-v outcome variables (F₀—theoretical maximal force, V₀—maximal unloaded velocity, P_max—maximal power output, F-v_slope—the slope of F-v relationship) calculated from CMJs compared to FW squats (all p < 0.01). Significant positive moderate correlations between the tasks were found for F₀ and P_max (r = 0.323–0.378, p = 0.018–0.045). In comparison to F-v outcome variables obtained in FW squats, higher correlations were found between F-v outcome variables calculated from CMJs and CoD tests. The only significant correlation in F-v outcome variables calculated from FW squats was found between P_max and short KST time. For all CoD tests, only one F-v predictor was included; more specifically—CMJ-F₀ for CoD 90°, CoD 180° and t-test, and FW-P_max for short KST performance. To conclude, our results showed that F-v relationship between CMJs and FW squats differed significantly and cannot be used interchangeably for F-v profiling. Moreover, we confirmed that high force and power production is important for the successful performance of general and karate specific CoD tasks.

The Post-Activation Potentiation Effects on Sprinting Abilities in Junior Tennis Players

Objective: This study aimed to compare the acute effects of a full squat (SQ) or hip thrust (HT) with two different loading intensities (60% and 85% 1 RM) on sprint ability in junior male tennis players. Methods: Nineteen tennis players were included in this research. They underwent four different experimental conditions: HT at 60% 1 RM, HT at 85% 1 RM, SQ at 60% 1 RM, or SQ at 85%. The force–velocity (F–V) profile was used to assess tennis players’ sprint acceleration ability before and after applying the conditioning stimulus. The variables registered were as follows: 5 m test (5 m), 10 m test (10 m), maximum theoretical force (F₀), maximum power (P_max), and the maximal ratio of horizontal-to-resultant force (RF_peak). Results: Significant improvements in 5 m, P_max, and RF_peak were observed when the conditioning stimulus was performing one set of seven reps of HT at 60% 1 RM. When the activation protocol was one set of seven reps of SQ at 60% 1 RM, significant improvements in 5 m, 10 m, F₀, P_max (N), and RF_peak were detected. Additionally, performing one set of three reps of SQ at 85% 1 RM as an activation protocol provided significant improvements in F₀. Conclusion: The use of HT and SQ with a load of 60% 1 RM improved the sprint F–V profile components related to the acceleration phase of the sprint in junior tennis players. Using intensity loads of 85% 1 RM is not adequate to increase acute sprint performance in this population. HT presents a higher transferability to sprinting in the first 5 m of sprinting, whereas SQ provides acute improvements in different sprinting phases.

The Effect of 16 Weeks of Lower-Limb Strength Training in Jumping Performance of Ballet Dancers

Jumping ability is considered a determinant of performance success. It is identified as one of the predictors and talent identification in many sports and dance. This study aimed to investigate the effect of 16 weeks of lower-limb strength training on the jumping performance of ballet dancers. A total of 24 participants from the same dance school were randomly selected in the control group [CG; n = 10; aged 13.00 (1.49) years; 43.09 (9.48) kg and 1.53 (0.11) m] and the intervention group [IG; n = 14; aged 12.43 (1.45) years; 38.21 (4.38) kg and 1.51 (0.07) m], evaluated before and after the applied strength training program mainly using the body weight of each participant. Jump performance was assessed using MyJump2, a scientifically validated mobile phone app. Intergroup and intragroup comparisons were assessed, and the magnitude of change was calculated using the effect size (ES). While CG significantly decreased the relative power over time (p < 0.001, ES = −0.29: small), results from the intragroup comparisons suggest that IG significantly increased the countermovement jump (CMJ) height (p < 0.001, ES = 1.21: large), the relative force (p < 0.001, ES = 0.86: moderate), maximal velocity (p < 0.001, ES = 1.15: moderate), and relative power (p < 0.001, ES = 1.37: large). We concluded that a 16-week strength training program of lower limbs is an effective way to improve CMJ height in young dancers. Supplementary strength training appears to be the determinant for the improvement of the jumping performance of ballet dancers.

Comparison of movement velocity and force-velocity parameters using a free video analysis software and a linear position transducer during unilateral and bilateral ballistic leg press

Study aim: This study compared movement velocity and force-velocity profile parameters measured by a free video analysis software program, with the use of a high-speed video recording, and a validated linear position transducer (LPT).

Material and methods: Ten team-sports athletes performed double-leg and single-leg ballistic lower limb extensions on a leg press machine against a wide range of resistive loads. Each repetition was recorded by the LPT a high-speed camera (300 fps), and later analysed with a free video analysis software program.

Results: Mean and peak movement velocity presented high reliability (ICC: 0.990 and 0.988, p < 0.001) and agreement between the two measuring systems (systematic bias: –0.06 ± 0.04 and –0.01 ± 0.03 m/s, respectively). Force-velocity profile parameters were also similar: maximum velocity at zero load (Vo: 1.79 ± 0.15 vs. 1.78 ± 0.12 m/s, p = 0.64), slope (b: –1585 ± 503 vs. –1562 ± 438 N · s/m, p = 0.43), maximum force at zero velocity (Fo: 2835 ± 937 vs. 2749 ± 694 N, p = 0.41) and maximum power (1274 ± 451 vs 1214 ± 285 W, p = 0.38). Both measuring systems could similarly detect the individual force or velocity deficit (p=0.91).

Conclusion: In conclusion, a free video analysis software combined with a high-speed camera was shown to be a reliable, accurate, low bias and cost-effective method in velocity-based testing.

Quantitative Analysis of Performance Recovery in Semi-Professional Football Players after the COVID-19 Forced Rest Period

This study proposes the instrumental analysis of the physiological and biomechanical adaptation of football players to a fatigue protocol during the month immediately after the COVID-19 lockdown, to get insights into fitness recovery. Eight male semi-professional football players took part in the study and filled a questionnaire about their activity during the lockdown. At the resumption of activities, the mean heart rate and covered distances during fatiguing exercises, the normalized variations of mean and maximum exerted power in the Wingate test and the Bosco test outcomes (i.e., maximum height, mean exerted power, relative strength index, leg stiffness, contact time, and flight time) were measured for one month. Questionnaires confirmed a light-intensity self-administered physical activity. A significant effect of fatigue (Wilcoxon signed-rank test p < 0.05) on measured variables was confirmed for the four weeks. The analysis of the normalized variations of the aforementioned parameters allowed the distinguishing of two behaviors: downfall in the first two weeks, and recovery in the last two weeks. Instrumental results suggest a physiological and ballistic (i.e., Bosco test outcomes) recovery after four weeks. As concerns the explosive skills, the observational data are insufficient to show complete recovery.

The Potentiating Response to Accentuated Eccentric Loading in Professional Football Players

The purpose of this study was to assess the acute effect of Accentuated Eccentric Loading (AEL) on countermovement jump (CMJ) height, peak power output (PPO) and peak velocity in male professional footballers using loads of 20% or 40% of body mass (AEL20 or AEL40, respectively). Twenty-three male professional football players (age 24 ± 4.5 years, range 18–34 years; body mass 80.21 ± 8.4 kg; height 178.26 ± 7.62 cm) took part in a randomised, cross-over design to test the potentiating responses of two AEL conditions (AEL20 and AEL40) versus a body weight control group (CON). Mean loads for the two conditions were 15.84 ± 1.70 kg (AEL20) and 31.67 ± 3.40 kg (AEL40). There was no significant difference between the three conditions for jump height (p = 0.507, η²_G = 0.022). There were significant differences in peak power between the groups (p = 0.001, η²_G = 0.154). Post hoc analysis with Bonferroni adjustment showed significantly higher peak power for both AEL conditions compared to the control group, but no significant differences between AEL conditions (CON vs. AEL20, p = 0.029, 95% CI −1016.735, −41.815, Cohen’s d = −0.56; CON vs. AEL40, p = 0.001, 95% CI −1244.995, −270.075, Cohen’s d = −0.81; AEL20 vs. AEL40, p = 0.75, 95% CI −715.720, 259.201, Cohen’s d = −0.24). There was no significant difference between the three conditions for peak velocity (p = 0.269, η²_G = 0.046). AEL using either 20% or 40% of body mass may be used to increase peak power in the countermovement jump in well-trained professional football players.

Effects of Resistance Training With Constant, Inertial, and Combined Loads on Muscle Power and Strength Output

The aim of this study was to investigate the resistance-specific gains in muscle power and strength (1RM) following the training of maximum bench-press throws (BPT) against constant, inertial, and combined resistance. Forty-eight male participants (age 20.5 ± 2.0 years) were randomly assigned to the constant, inertial, combined resistance, or control group. Participants underwent 8 weeks of training of BPT against the loads that corresponded to the different effects of mass of 40 kg (∼50% of 1RM). The gains in average and maximum power, and 1RM were significant in all experimental groups (P < 0.01), but not in the control group (P > 0.1). Relative gains in the average (26.3 ± 9.8%) and maximum power (25.2 ± 9.8%) were larger than that in the 1RM (mean 7.2 ± 6.9%; both P < 0.001). The gains in the average (F 4, 66 = 6.0; P < 0.01) and maximum power (F 4, 66 = 4.7; P < 0.01) were higher when tested against the training-specific resistance than when tested against the remaining two resistance types. Differences in 1RM among experimental groups were not significant (P = 0.092). The most important and rather novel finding of the study is that the training against the weight and inertial resistance, and their combination results in resistance-specific gains in muscle power, although the overall gains muscle strength and power remain comparable across the training protocols.

Assessment and Evaluation of Force–Velocity Variables in Flywheel Squats: Validity and Reliability of Force Plates, a Linear Encoder Sensor, and a Rotary Encoder Sensor

Research into flywheel (FW) resistance training and force–velocity–power (F–v–P) profiling has recently gained attention. Ground reaction force (GRF) and velocity (v) during FW squats can be predicted from shaft rotational data. Our study aimed to compare the inter-set reliability of GRF, v, and F–v–P relationship output variables calculated from force plates and linear encoder (presumed gold-standard) and rotary encoder data. Fifty participants performed two sets of FW squats at four inertias. Peak and mean concentric and eccentric GRF, v, and F–v–P outcomes from mean variables during the concentric phase of the squat were calculated. Good to excellent reliability was found for GRF and v (ICC > 0.85), regardless of the measure and the variable type. The F–v–P outcomes showed moderate to good reliability (ICC > 0.74). Inter-measure bias (p < 0.05) was found in the majority of GRF and v variables, as well as for all the calculated F–v–P outcomes (trivial to large TEs) with very large to perfect correlations for v (r 0.797–0.948), GRF (r 0.712–0.959), and, finally, F–v–P outcomes (ICC 0.737–0.943). Rotary encoder overestimated the force plates and linear encoder variables, and the differences were dependent on the level of inertia. Despite high reliability, FW device users should be aware of the discrepancy between the measures.

Characterising initial sprint acceleration strategies using a whole-body kinematics approach

Sprint acceleration is an important motor skill in team sports, thus consideration of techniques adopted during the initial steps of acceleration is of interest. Different technique strategies can be adopted due to multiple interacting components, but the reasons for, and performance implications of, these differences are unclear. 29 professional rugby union backs completed three maximal 30 m sprints, from which spatiotemporal variables and linear and angular kinematics during the first four steps were obtained. Leg strength qualities were also obtained from a series of strength tests for 25 participants, and 13 participants completed the sprint protocol on four separate occasions to assess the reliability of the observed technique strategies. Using hierarchical agglomerative cluster analysis, four clear participant groups were identified according to their normalised spatiotemporal variables. Whilst significant differences in several lower limb sprint kinematic and strength qualities existed between groups, there were no significant between-group differences in acceleration performance, suggesting inter-athlete technique degeneracy in the context of performance. As the intra-individual whole-body kinematic strategies were stable (mean CV = 1.9% to 6.7%), the novel approach developed and applied in this study provides an effective solution for monitoring changes in acceleration technique strategies in response to technical or physical interventions.

Sprint and Jump Mechanical Profiles in Academy Rugby League Players: Positional Differences and the Associations between Profiles and Sprint Performance

This cross-sectional study evaluated the sprint and jump mechanical profiles of male academy rugby league players, the differences between positions, and the associations between mechanical profiles and sprint performance. Twenty academy rugby league players performed 40-m sprints and squat jumps at increasing loads (0-80 kg) to determine individual mechanical (force-velocity-power) and performance variables. The mechanical variables (absolute and relative theoretical maximal force-velocity-power, force-velocity linear relationship, and mechanical efficiency) were determined from the mechanical profiles. Forwards had significantly (p < 0.05) greater vertical and horizontal force, momentum but jumped lower (unloaded) and were slower than backs. No athlete presented an optimal jump profile. No associations were found between jump and sprint mechanical variables. Absolute theoretical maximal vertical force significantly (p < 0.05) correlated (r = 0.71-0.77) with sprint momentum. Moderate (r = -0.47) to near-perfect (r = 1.00) significant associations (p < 0.05) were found between sprint mechanical and performance variables. The largest associations shifted from maximum relative horizontal force-power generation and application to maximum velocity capabilities and force application at high velocities as distance increased. The jump and sprint mechanical profiles appear to provide distinctive and highly variable information about academy rugby league players' sprint and jump capacities. Associations between mechanical variables and sprint performance suggest horizontal and vertical profiles differ and should be trained accordingly.

The difference between squat jump and countermovement jump in 770 male and female participants from different sports

Traditionally, a larger difference between countermovement (CMJ) and squat jump (SJ) was seen as beneficial, as it reflects the ability to utilize the stretch-shortening cycle. However, strong arguments have been made that this might not always be the case, as larger differences between the jumps could also suggest higher muscle-tendon slack, or poor capability to take this slack up quickly. The purpose of this study was to explore SJ and CMJ, as well as the CMJ to SJ difference (CMJSJ_Diff) in 9 groups of young athletes. In total, 712 athletes from various disciplines (mean age range: 15.7-36.3 years) and 58 physical education students (mean age: 19.6 years) participated in the study. The major finding of this study was that the groups that showed better SJ and CMJ performance did not show the larger CMJSJ_Diff. For instance, SJ and CMJ heights were highest in short-distance runners and lowest in long-distance runners, while the largest and smallest CMJSJ_Diff was shown in physical education students and speed skaters, respectively. Male athletes had a higher CMJSJ_Diff than female athletes, but the difference was very small. While a larger CMJSJ_Diff has been traditionally associated viewed as positive, our results could indicate both superior ability to utilize the stretch-shortening cycle, as well as poor ability of rapid force development and excessive muscle slack. Further studies are needed to directly investigate the associations between CMJSJ_Diff and indicators of athletic performance.

Examination of the Sprinting and Jumping Force-Velocity Profiles in Young Soccer Players at Different Maturational Stages

The aim was to determine the relationships among components of the force-velocity (F-V) profiles in jumping and sprinting, with both biological and chronological ages in 89 young soccer players belonging to categories from U10 to U18. Participants performed countermovement jumps (CMJ) and 20-m sprint tests. F-V components assessed were associated with both maturity offset and chronological age, using correlation and multiple linear regression analyses. Horizontal (i.e., maximal theoretical force [F0] and velocity [V0], maximal power [Pmax] and F-V slope) and vertical (i.e., [F0] and [Pmax]) F-V components displayed very large correlations (i.e., 0.79 ≤ r ≤ 0.92) with both chronological age and maturity offset. The combination of sprinting Pmax and training experience and jumping F0 and training experience explained up to 94% of the variances in maturity offset and chronological age. Furthermore, similar correlations were found between sprinting and jumping performances, and components of the F-V profiles, and both maturity offset and chronological age. Identification of vertical jump and sprint mechanical determinants may assist in strengthening those components of the F-V profile which are weaker throughout the training process. Sprinting and jumping capabilities can be indistinctly monitored with respect to their chronological age or maturity offset in young soccer players.

Predictive Validity of the Snatch Pull Force-Velocity Profile to Determine the Snatch One Repetition-Maximum in Male and Female Elite Weightlifters

BACKGROUND

The prediction of one repetition-maximum (1RM) performance from specific tests is highly relevant for the monitoring of training in weightlifting. Therefore, this study aimed at examining the predictive validity of the theoretical 1RM snatch (snatch_th) computed from the two-point snatch pull force-velocity relationship (FvR₂) to determine actual snatch 1RM performance in elite weightlifters.

METHODS

Eight (three female, five male) elite weightlifters carried out a 1RM snatch test followed by a snatch pull test with loads of 80% and 110% of the previously determined 1RM snatch. Barbell kinematics were determined for all lifts using video-tracking. From the snatch pull barbell kinematics, the snatch pull FvR₂ was modeled and the snatch_th was calculated.

RESULTS

The main findings indicated a non-significant (p = 0.706) and trivial (d = 0.01) mean difference between the actual 1RM snatch performance and the snatch_th. Both measures showed an extremely large correlation (r = 0.99). The prediction accuracy of the actual 1RM snatch from snatch_th was 0.2 ± 1.5 kg (systematic bias ± standard deviation of differences).

CONCLUSIONS

This study provides a new approach to estimate 1RM snatch performance in elite weightlifters using the snatch pull FvR₂. The results demonstrate that the snatch_th-model accurately predicts 1RM snatch performance.

The force-velocity profile as determinant of spike and serve ball speed in top-level male volleyball players

Understanding the relationship between mechanical variables derived from actions such as jumping, sprinting, or ballistic bench press throwing and sport-specific performance moves is of scientific and practical interest for strength and conditioning coaches for improving training programs. We examined the association between mechanical variables derived from the force-velocity (FV) profiles of the aforementioned actions and spike and serve ball speeds in elite volleyball players. Twenty-two male elite volleyball players (age: 24.3 ± 4.5 years; height: 1.89 ± 0.06 m; body mass: 86.3 ± 8.6 kg) were tested in two sessions. Squatting, sprinting, and bench press throwing FV profiles were determined in the first session, while spike and serve ball speeds were assessed in the second session. The theoretical maximal force (F0) of vertical jumping, the theoretical maximal velocity of sprinting, and the F0 of bench press throwing in ascending order, were strongly associated (rs range 0.53-0.84; p<0.05) with spike and serve ball speeds. These mechanical variables explained 20%-36% of the variability in spike and serve ball speeds, with a greater influence on the serve speed. These results suggest that assessing jumping, sprinting, and bench press throwing force-velocity profiles might help provide player-specific training programs and optimize performance in these technical-tactical actions in male elite volleyball players.

Force-velocity profiling in athletes: Reliability and agreement across methods

The aim of the study was to examine the test-retest reliability and agreement across methods for assessing individual force-velocity (FV) profiles of the lower limbs in athletes. Using a multicenter approach, 27 male athletes completed all measurements for the main analysis, with up to 82 male and female athletes on some measurements. The athletes were tested twice before and twice after a 2- to 6-month period of regular training and sport participation. The double testing sessions were separated by ~1 week. Individual FV-profiles were acquired from incremental loading protocols in squat jump (SJ), countermovement jump (CMJ) and leg press. A force plate, linear encoder and a flight time calculation method were used for measuring force and velocity during SJ and CMJ. A linear regression was fitted to the average force and velocity values for each individual test to extrapolate the FV-variables: theoretical maximal force (F0), velocity (V0), power (Pmax), and the slope of the FV-profile (SFV). Despite strong linearity (R2>0.95) for individual FV-profiles, the SFV was unreliable for all measurement methods assessed during vertical jumping (coefficient of variation (CV): 14-30%, interclass correlation coefficient (ICC): 0.36-0.79). Only the leg press exercise, of the four FV-variables, showed acceptable reliability (CV:3.7-8.3%, ICC:0.82-0.98). The agreement across methods for F0 and Pmax ranged from (Pearson r): 0.56-0.95, standard error of estimate (SEE%): 5.8-18.8, and for V0 and SFV r: -0.39-0.78, SEE%: 12.2-37.2. With a typical error of 1.5 cm (5-10% CV) in jump height, SFV and V0 cannot be accurately obtained, regardless of the measurement method, using a loading range corresponding to 40-70% of F0. Efforts should be made to either reduce the variation in jumping performance or to assess loads closer to the FV-intercepts. Coaches and researchers should be aware of the poor reliability of the FV-variables obtained from vertical jumping, and of the differences across measurement methods.

Strength-Endurance: Interaction Between Force-Velocity Condition and Power Output

Context

Strength-endurance mainly depends on the power output, which is often expressed relative to the individual’s maximal power capability (P_max). However, an individual can develop the same power, but in different combinations of force and velocity (force-velocity condition). Also, at matched power output, changing the force-velocity condition results in a change of the velocity-specific relative power (P_maxv), associated with a change in the power reserve. So far, the effect of these changing conditions on strength-endurance remains unclear.

Purpose

We aimed to test the effects of force-velocity condition and power output on strength-endurance.

Methods

Fourteen sportsmen performed (i) force- and power-velocity relationships evaluation in squat jumps and (ii) strength-endurance evaluations during repeated squat jump tests in 10 different force-velocity-power conditions, individualized based on the force- and power-velocity relationships. Each condition was characterized by different (i) relative power (%P_max), (ii) velocity-specific relative power (%P_maxv), and (iii) ratio between force and velocity (R_Fv). Strength-endurance was assessed by the maximum repetitions (SJ_Rep), and the cumulated mechanical work (W_tot) performed until exhaustion during repeated squat jump tests. Intra and inter-day reliability of SJ_Rep were tested in one of the 10 conditions. The effects of %P_max, %P_maxv, and R_Fv on SJ_Rep and W_tot were tested via stepwise multiple linear regressions and two-way ANOVAs.

Results

SJ_Rep exhibited almost perfect intra- and inter-day reliability (ICC=0.94 and 0.92, respectively). SJ_Rep and W_tot were influenced by %P_maxv and R_Fv (R² = 0.975 and 0.971; RSME=0.243 and 0.234, respectively; both p < 0.001), with the effect of R_Fv increasing with decreasing %P_maxv (interaction effect, p = 0.03). %P_max was not considered as a significant predictor of strength-endurance by the multiple regressions analysis. SJ_Rep and W_tot were higher at lower %P_maxv and in low force-high velocity conditions (i.e., lower R_Fv).

Conclusion

Strength-endurance was almost fully dependent on the position of the exercise conditions relative to the individual force-velocity and power-velocity relationships (characterized by %P_maxv and R_Fv). Thus, the standardization of the force-velocity condition and the velocity-specific relative power should not be overlooked for strength-endurance testing and training, but also when setting fatiguing protocols.

Decisive Factors for a Greater Performance in the Change of Direction and Its Angulation in Male Basketball Players

A study was made to initially evaluate whether the age category directly could influence anthropometric measurements, functional movement tests, linear sprint (30 m) and strength. Moreover, and as the main purpose, this study aimed to examine the relationship between the time execution and angles in different changes of direction (COD) test with the analyzed sport performance variables. A total sample of 23 basketball players (age: 17.5 ± 2.42 years; height: 184.6 ± 6.68 cm; body weight: 78.09 ± 11.9 kg). Between-groups’ comparison explored the differences between basketball categories (Junior, n = 12; Senior, n = 11). The COD variables were divided by the time execution into low responders (LR) and high responders (HR) to establish comparisons between groups related to COD time execution. Pearson’s correlation coefficient was used to establish correlations between different CODs and sport performance variables. The results showed a greater influence of age category upon COD performance, especially when the cutting angle was sharper (7.05% [Confidence limits (CL) 90%: 2.33; 11.99]; Quantitative chances (QC) 0/2/98), in which athletes need greater application of strength. Moreover, the sharper the angle or the larger the number of cuts made, the greater the relationship with the vertical force–velocity profile (−42.39 [CL 90%: −57.37; −22.16]; QC 100/0/0%). Thus, the usefulness of the f–v profile to implement training programs that optimize the f–v imbalance and the improvement of the COD performance in basketball players is suggested.

Leg extension force-velocity imbalance has negative impact on sprint performance in ball-game players

Ballistic actions are imperative in sports where performance depends on power production across a relevant range of contraction- and movement velocities. Force-velocity-power (FvP‾) profiling provides information regarding neuromuscular capabilities and vertical performances, but knowledge regarding its associative value towards horizontal movements is scarce. Therefore, we conducted FvP‾ profiling and analysed associations with uni- and multidirectional ballistic performance tasks in 27 international- to national-level athletes (18.9 ± 2.6 years, 182.9 ± 7.1 cm and 79.2 ± 11.9 kg). Low to moderate correlations were observed between theoretical maximal power (P-max) and horizontal acceleration (R = -0.43), speed (R = -0.64), sprint (R = -0.60) and agility (R = -0.59) performances. Force-velocity imbalance (Fv_IMB) significantly (P ≤ 0.05) strengthened the correlations towards sprinting ability (from -0.60 to -0.74) and agility (from -0.59 to -0.68), however, both correlations remaining weaker than for jumping performances (R = 0.78-0.86). In conclusion, FvP‾ profiling provides information of importance for horizontal and vertical performances with a significant positive effect of P-max, but negative effect of Fv_IMB. Assessment of lower-extremity neuromuscular capabilities through FvP‾ profiling and associated development of training programmes targeting compensation of either force- or velocity deficit may benefit the ability to utilise a given power potential.

Does the initial level of horizontal force determine the magnitude of improvement in acceleration performance in rugby?

This study aimed to observe the effect of 8 weeks of resisted sled training (RST), with optimal loading for maximal power output production and initial levels of force, on the magnitude of improvement in sprint performance and individual sprint mechanical outputs in female amateur rugby union players. The study examined the horizontal Power-Force-Velocity profile (P-F-V profile), which provides a measure of the athlete's individual balance between force and velocity capabilities (S_fv), theoretical maximum force (F₀), theoretical maximum velocity (V₀), maximum power (P_max), the maximum ratio of force (Rf_max) and rate of decrease in ratio of force (D_rf). Thirty-one participants (age = 23.7 ± 3.3years, BM = 69 ± 9Kg, height = 167.5 ± 5.2 cm) were divided into a control group and two experimental groups; forwards (FG) and backs (BG). For 8 consecutive weeks (16 sessions), all groups performed the same training programme: 2 sets of 5 × 30 m, but athletes assigned to FG and BG ran towing a resisted sled attached to their waists, with optimal loading for maximal power output production. Both FG and BG significantly improved (p ≤ 0.05) in 5 and 20 m sprint performance, and in the mechanical properties related to the horizontal P-F-V profile. The correlation between the initial level of horizontal strength and the magnitude of improvement in P_max also suggests that higher levels of horizontal force may lead to greater adaptations in RST. The P-F-V profile is a useful field method for identifying the weakest mechanical variable in rugby players during sprinting and enabling the prescription of individualized training programmes according to specific running performance.

Differences in Utilization of Lower Limb Muscle Power in Squat Jump With Positive and Negative Load

Jump performance is related to the ability of lower limb muscles to produce power during the push-off phase. However, it is not known if the power associated with the action of active and passive elements of the lower limb muscles change significantly in jumps with positive and negative loads. In this study, the power associated with the action of passive and active components of lower limb muscles as a whole in squat jumps (SJ) with increase and decrease in the external load is analyzed Fourteen trained male subjects (22.5 ± 2.1 years; 176.5 ± 5.4 cm; 75.8 ± 5.8 kg; BMI 24.3 ± 1.8) performed SJ on a force plate. A functional electromechanical dynamometer (FEMD) system was used to change the external load in a range of -30 to +30% of the subject's body weight. A model comprising a mass, a spring, an active element, and a damper was used. We applied an optimization principle to determine power in center of mass (CoM) (ptot), the powers associated with active element (pact), damper (pƔ), and spring (pk) during the push-off phase. Significant differences between loading conditions for each variable were tested by repeated-measures one-way ANOVA with Bonferroni post hoc analysis, p < 0.05. Shapes of the average curves for instantaneous variation of pact, pƔ, pk, and ptot during push-off with positive loads were closer to 0% than with negative loads. As the load increased, maximum values of ptot, pƔ, and pk decreased. Only with a negative load of -30% did ptot increase significantly, this was not accompanied by changes in pact, pƔ, and pk. The load of one's own body provides conditions for develop high pact peaks, although the maximum ptot is not achieved in that condition. The increase in negative loads produces a significant increase in ptot, but not in pact and can be interpreted as a situation in which the power delivered to the system by the action of active components is better used. The SJ with positive load, although more similar to the instantaneous changes that occur to the SJ with body weight are not gestures where high power is developed.

Validity and reliability of force-velocity outcome parameters in flywheel squats

Our study was designed to check the reliability of force-velocity (F-v) relationship outcome measures using flywheel (FW) squats. The main objectives at the primary level were to test intra-session reliability of mechanical parameters for ten equidistant FW loads, and at the secondary level, to test reliability and validity of the F-v relationship outcome measures in case any possible reduction in used loads and number of loads - compared to the 10-load method as a reference - is administered. Twenty-six subjects performed two sets of five squats with FW loads in the range 0.025-0.25 kg∙m2. Averaging six consecutive repetitions obtained ICC2.k > 0.9 for mean force and mean velocity results. Consecutively averaged parameters at the primary level showed excellent inter-set reliability (ICC2.1 > 0.9). The inverse F-v relationship was strong (R2 = 0.96). At the secondary level, Bland-Altman statistics showed decreasing bias and limits of agreement in combination with more loads. Theoretical maximal force and power showed smaller bias as F-v slope and theoretical maximal velocity for three loads or more. Four loads (0.025, 0.075, 0.225 and 0.25 kg∙m2) lowered bias to a 5% in relation to the reference F-v slope. In conclusion, six repetitions are required to obtain trustworthy force and velocity results. The results will contribute to standardising the methodology for assessing the mechanical capacities of leg muscles using FW resistance. Moreover, assessing individual F-v profile with reduced protocol may be a less fatiguing tool for prescribing exercise intensity and for assessing training adaptations.

When Jump Height is not a Good Indicator of Lower Limb Maximal Power Output: Theoretical Demonstration, Experimental Evidence and Practical Solutions

Lower limb external maximal power output capacity is a key physical component of performance in many sports. During squat jump and countermovement jump tests, athletes produce high amounts of mechanical work over a short duration to displace their body mass (i.e. the dimension of mechanical power). Thus, jump height has been frequently used by the sports science and medicine communities as an indicator of the power output produced during the jump and by extension, of maximal power output capacity. However, in this article, we contend that squat jump and countermovement jump height are not systematically good indicators of power output produced during the jump and maximal power output capacity. To support our opinion, we first detail why, theoretically, jump height and maximal power output capacity are not fully related. Specifically, we demonstrate that individual body mass, push-off distance, optimal loading and the force-velocity profile confound the jump height-power relationship. We also discuss the relationship between squat jump or countermovement jump height and maximal power output capacity measured with a force plate based on data reported in the literature, which added to our own experimental evidence. Finally, we discuss the limitations of existing practical solutions (regression-based estimation equations and allometric scaling), and advocate using a valid, reliable and simple field-based procedure to compute individual power output produced during the jump and maximal power output capacity directly from jump height, body mass and push-off distance. The latter may allow researchers and practitioners to reduce bias in their assessment of lower limb mechanical power output by using jump height as an input with a simple yet accurate computation method, and not as the first/only variable of interest.

Cluster vs. traditional training programmes: changes in the force-velocity relationship

This randomised controlled study examined the force-velocity relationship changes (force and velocity axis intercepts, slope and estimated maximum power) in response to 5-week training programmes differing in the set configuration. For each session, the traditional group performed 4 sets of 8 repetitions with 5 min of rest between sets and exercises, while the cluster group completed 16 sets of 2 repetitions with 1 min of rest between sets and 5 min between exercises. Both programmes were performed with the 10-repetition maximum load, including bench press, parallel squat, lat pull-down and leg curl exercises. Individual force-velocity profiles were obtained for bench press and squat using a linear velocity transducer before and after the intervention, along with lactate and mechanical performance during the intervention. Results showed in bench press similar changes of the force-velocity profile after both protocols (no shift of the slope and higher force and velocity axis intercept values). For the squat, significant changes in the slope (P = 0.001) and the velocity intercept (P = 0.002) towards a velocity profile were observed after cluster but not after traditional training. These results suggest that set configuration may modulate changes of force-velocity relationship, especially for squat.

Dynamic Force Production Capacities Between Coronary Artery Disease Patients vs. Healthy Participants on a Cycle Ergometer

Background

The force-velocity-power (FVP) profile is used to describe dynamic force production capacities, which is of great interest in training high performance athletes. However, FVP may serve a new additional tool for cardiac rehabilitation (CR) of coronary artery disease (CAD) patients. The aim of this study was to compare the FVP profile between two populations: CAD patients vs. healthy participants (HP).

Methods

Twenty-four CAD patients (55.8 ± 7.1 y) and 24 HP (52.4 ± 14.8 y) performed two sprints of 8 s on a Monark cycle ergometer with a resistance corresponding to 0.4 N/kg × body mass for men and 0.3 N/kg × body mass for women. The theoretical maximal force (F₀) and velocity (V₀), the slope of the force-velocity relationship (S_fv) and the maximal mechanical power output (P_max) were determined.

Results

The P_max (CAD: 6.86 ± 2.26 W.kg^–1 vs. HP: 9.78 ± 4.08 W.kg^–1, p = 0.003), V₀ (CAD: 5.10 ± 0.82 m.s^–1 vs. HP: 5.79 ± 0.97 m.s^–1, p = 0.010), and F₀ (CAD: 1.35 ± 0.38 N.kg^–1 vs. HP: 1.65 ± 0.51 N.kg^–1, p = 0.039) were significantly higher in HP than in CAD. No significant difference appeared in S_fv (CAD: −0.27 ± 0.07 N.kg^–1.m.s^–1 vs. HS: −0.28 ± 0.07 N.kg^–1.m.s^–1, p = 0.541).

Conclusion

The lower maximal power in CAD patients was related to both a lower V₀ and F₀. Physical inactivity, sedentary time and high cardiovascular disease (CVD) risk may explain this difference of force production at both high and low velocities between the two groups.

Effects of two drop-jump protocols with different volumes on vertical jump performance and its association with the force-velocity profile

PURPOSE

This study aimed to evaluate the changes in countermovement jump (CMJ) height after two drop-jump (DJ) protocols with different volumes, and to explore the possibility of predicting the changes in CMJ height based on the vertical force-velocity (F-v) profile.

METHOD

Thirty-four male athletes (age: 21.9 ± 2.0 years) were tested on three occasions. The F-v profile during the CMJ exercise was determined in the first session. Two DJ protocols (low-volume [1 set of 5 DJ trials from a 30 cm height] and high-volume [3 sets of 5 DJ trials from a 30 cm height]) were randomly performed during the second and third sessions, and the unloaded CMJ height was evaluated before (Pre), 4 min (Post4), 8 min (Post8), and 12 min (Post12) after the DJ protocol.

RESULTS

CMJ height was significantly higher at Post4 (2.5 cm [95% confidence interval (CI) = 2.0-3.0 cm]; ES = 0.35), Post8 (2.1 cm [95% CI = 1.4-2.8 cm]; ES = 0.29) and Post12 (2.2 cm [95% CI = 1.4-3.0 cm]; ES = 0.30) compared to Pre. The only significant interaction (protocol × time) was caused by a higher increment in CMJ height at Post4 for the low-volume (8.1 ± 3.7%) compared to the high-volume (5.8 ± 3.9%) protocol. The F-v profile did not explain a significant part of the change in CMJ height (variance explained < 10%).

CONCLUSIONS

These results suggest that low-volume DJ protocols could be more efficient to acutely increase CMJ performance, while the change in CMJ height was not affected by the F-v profile.

Relationship between Cyclic and Non-Cyclic Force-Velocity Characteristics in BMX Cyclists

Especially for bicycle motocross (BMX) cyclists, transfer of muscular force-velocity (Fv) characteristics between common strength training exercises and cycling is important. This study investigated the relationship between Fv characteristics in a common training exercise (squat jumps) and a sport-specific task (cycling) in high-level BMX racers by exploring the degree to which Fv and torque–cadence (Tc) characteristics correspond. Twelve BMX racers performed an Fv (multiple loaded squat jump) and two Tc tests (ramp starts and flat-ground sprints). Results revealed very large correlations between F0 and Tor0 start (r = 0.77) and between Pmax jump and Pmax start (r = 0.85). On the other hand, the relationships between v0 and Cad0 start (r = –0.25) and between SFv and STc start (r = –0.14) were small and negative. Similar results were observed for sprints. Based on dichotomous classifications (greater or less than group median), several discrepancies occurred, particularly for the profile slopes and high-speed variables. Thus, we recommend performing both jump-based and cycling-specific Fv testing. Of additional note, Tc characteristics on flat ground were similar to, but slightly different from those on the start ramp. Therefore, where possible, Tc tests should be carried out on a ramp.

Is Test Standardization Important when Arm and Leg Muscle Mechanical Properties are Assessed through the Force-Velocity Relationship?

The force‐velocity (F‐V) relationship observed in multi‐joint tasks proved to be strong and approximately linear. Recent studies showed that mechanical properties of muscles: force (F), velocity (V) and power (P) could be assessed through the F‐V relationship although the testing methods have not been standardized. The aim of the present study was to evaluate and compare F‐V relationships assessed from two tests performed on a modified Smith machine that standardizes kinematics of the movement pattern. Fifteen participants were tested on the maximum performance bench press throws and squat jumps performed against a variety of different loads. In addition, their strength properties were assessed through maximum isometric force (Fiso) and one repetition maximum (1 RM). The observed individual F‐V relationships were exceptionally strong and approximately linear (r = 0.98 for bench press throws; r = 0.99 for squat jumps). F‐V relationship parameter depicting maximum force (F0) revealed high correlations with both Fiso and 1 RM indicating high concurrent validity (p < 0.01). However, the generalizability of F‐V relationship parameters depicting maximum force (F0), velocity (V0) and power (P0) of the tested muscle groups was inconsistent and on average low (i.e. F0; r = ‐0.24) to moderate (i.e. V0 and P0; r = 0.54 and r = 0.64, respectively; both p < 0.05). We concluded that the F‐V relationship could be used for the assessment of arm and leg muscle mechanical properties when standard tests are applied, since the typical outcome is an exceptionally strong and linear F‐V relationship, as well as high concurrent validity of its parameters. However, muscle mechanical properties could be only partially generalized across different tests and muscles.

Force-Velocity Relationship in the Countermovement Jump Exercise Assessed by Different Measurement Methods

This study aimed to compare force, velocity, and power output collected under different loads, as well as the force-velocity (F-V) relationship between three measurement methods. Thirteen male judokas were tested under four loading conditions (20, 40, 60, and 80 kg) in the countermovement jump (CMJ) exercise, while mechanical output data were collected by three measurement methods: the Samozino's method (SAM), a force platform (FP), and a linear velocity transducer (LVT). The variables of the linear F-V relationship (maximum force [F0], maximum velocity [V0], F-V slope, and maximum power [P0]) were determined. The results revealed that (1) the LVT overestimated the mechanical output as compared to the SAM and FP methods, especially under light loading conditions, (2) the SAM provided the lowest magnitude for all mechanical output, (3) the F-V relationships were highly linear either for the SAM (r = 0.99), FP (r = 0.97), and LVT (r = 0.96) methods, (4) the F-V slope obtained by the LVT differed with respect to the other methods due to a larger V0 (5.28 ± 1.48 m·s-1) compared to the SAM (2.98 ± 0.64 m·s-1) and FP (3.06 ± 0.42 m·s-1), and (5) the methods were significantly correlated for F0 and P0, but not for V0 or F-V slope. These results only support the accuracy of the SAM and FP to determine the F-V relationship during the CMJ exercise. The very large correlations of the SAM and LVT methods with respect to the FP (presumed gold-standard) for the mean values of force, velocity and power support their concurrent validity for the assessment of mechanical output under individual loads.

Differences in the Force Velocity Mechanical Profile and the Effectiveness of Force Application During Sprint-Acceleration Between Sprinters and Hurdlers

This cross-sectional study aimed to compare the horizontal and vertical force-velocity profile between female sprinters and hurdlers. Twelve high-level athletes (6 sprinters and 6 hurdlers) participated in this investigation. The testing procedures consisted of two maximal 40-m sprints and five to six vertical jumps with additional loads. For the sprint-acceleration performance, the velocity-time data, recorded by a high-speed camera, was used to calculate the variables of the horizontal F-V profile (theoretical maximal values of force [HZT-F₀], velocity [HZT-V₀], power [HZT-Pmax], the proportion of the theoretical maximal effectiveness of force application in the antero-posterior direction [RFmax], and the rate of decrease in the ratio of horizontal force [DRF]). The best trial of each vertical jumping condition, obtained by an optical measurement system, was used to determine the components of the vertical F-V profile (theoretical maximal values of force [VTC-F₀], velocity [VTC-V₀], and power [VTC-Pmax]). The female sprinters showed higher statistical differences for HZT-Pmax (2.46 ± 0.67, d = 2.1, p = 0.004), HZT-V₀ (0.45 ± 0.18, d = 1.4, p = 0.03), and RFmax% (2.9 ± 0.9%, d = 1.8, p = 0.01) than female hurdlers. No statistical differences were observed for HZT-F₀ (0.69 ± 0.3, d = 1.15, p = 0.07), DRF% (−0.24 ± 0.4%, d = 0.3, p = 0.62), VTC-F₀ (−2.1 ± 3.8, d = 0.3, p = 0.59), VTC-V₀ (0.25 ± 0.31, d = 0.5, p = 0.45), and VTC-Pmax (1.75 ± 2.5, d = 0.4, p = 0.5). Female sprinters are able to apply higher horizontally-oriented forces onto the ground during the acceleration phase than female hurdlers.

Assessment of the force-velocity relationship during vertical jumps: influence of the starting position, analysis procedures and number of loads

This study aimed to compare the reliability and magnitude of the force-velocity (F-V) relationship parameters between the squat jumps performed from the 90° (SJ90) and self-preferred knee angle (SJ_pref). A secondary aim was to explore the effect of the analysis procedure (force platform [FP] and Samozino's [SAM] method) and the number of loads tested (three- and two-point methods) on the F-V relationships. Twelve men were tested in two sessions during the SJ90 and SJ_pref. Two identical blocks of jumps were performed in each session against three external loads. The F-V relationship parameters (maximum force, maximum velocity, F-V slope and maximum power) were determined at each block through the FP and SAM procedures using the data collected under three (three-point method) or only the two most distant loads (two-point method). The average coefficient of variation (CV) of the four F-V parameters revealed a higher reliability for the SJ90 compared to the SJ_pref (5.86% vs. 7.55%; CV_ratio= 1.29) with more pronounced differences using the FP (CV_ratio= 1.43) than the SAM procedure (CV_ratio= 1.14), and higher reliability for the SAM compared to the FP (6.14% vs. 7.27%; CV_ratio= 1.18). The SJ_pref and SAM procedures provided comparable or higher magnitude of the F-V relationship parameters than the SJ90 and FP, respectively. The three- and two-point methods revealed a comparable reliability and trivial differences in the magnitude of the F-V relationship parameters. The routine testing procedure of the F-V relationship could be simplified using the SJ_pref, the SAM procedure and the two-point method.

On the Shape of the Force-Velocity Relationship in Skeletal Muscles: The Linear, the Hyperbolic, and the Double-Hyperbolic

The shape of the force-velocity (F-V) relationship has important implications for different aspects of muscle physiology, such as muscle efficiency and fatigue, the understanding of the pathophysiology of several myopathies or the mechanisms of muscle contraction per se, and may be of relevance for other fields, such as the development of robotics and prosthetic applications featuring natural muscle-like properties. However, different opinions regarding the shape of the F-V relationship and the underlying mechanisms exist in the literature. In this review, we summarize relevant evidence on the shape of the F-V relationship obtained over the last century. Studies performed at multiple scales ranging from the sarcomere to the organism level have described the concentric F-V relationship as linear, hyperbolic or double-hyperbolic. While the F-V relationship has most frequently been described as a rectangular hyperbola, a large number of studies have found deviations from the hyperbolic function at both ends of the F-V relation. Indeed, current evidence suggests that the F-V relation in skeletal muscles follows a double-hyperbolic pattern, with a breakpoint located at very high forces/low velocities, which may be a direct consequence of the kinetic properties of myofilament cross-bridge formation. Deviations at low forces/high velocities, by contrast, may be related to a recently discovered, calcium-independent regulatory mechanism of muscle contraction, which may also explain the low metabolic cost of very fast muscle shortening contractions. Controversial results have also been reported regarding the eccentric F-V relationship, with studies in prepared muscle specimens suggesting that maximum eccentric force is substantially greater than isometric force, whereas in vivo studies in humans show only a modest increase, no change, or even a decrease in force in lengthening contractions. This review discusses possible reasons reported in the literature for these discrepant findings, including the testing procedures (familiarization, pre-load condition, and temperature) and a potential neural inhibition at higher lengthening velocities. Finally, some unresolved questions and recommendations for F-V testing in humans are reported at the end of this document.

Optimized training for jumping performance using the force-velocity imbalance: Individual adaptation kinetics

AIMS

We analysed the changes in force-velocity-power variables and jump performance in response to an individualized training program based on the force-velocity imbalance (FVimb). In particular, we investigated (i) the individual adaptation kinetics to reach the optimal profile and (ii) de-training kinetics over the three weeks following the end of the training program.

METHODS

Sixty subjects were assigned to four sub-groups according to their initial FVimb: high or low force-deficit (FD) and high or low velocity-deficit (VD). The duration of training intervention was set so that each individual reached their "Optimal force-velocity (F-v) profile". Mechanical and performance variables were measured every 3 weeks during the program, and every week after the end of the individualized program.

RESULTS

All subjects in the FD sub-groups showed extremely large increases in maximal theoretical force output (+30±16.6% Mean±SD; ES = 2.23±0.28), FVimb reduction (-74.3±54.7%; ES = 2.17±0.27) and large increases in jump height (+12.4±7.6%; ES = 1.45±0.23). For the VD sub-groups, we observed moderate to extremely large increases in maximal theoretical velocity (+15.8±5.1%; ES = 2.72±0.29), FVimb reduction (-19.2±6.9%; ES = 2.36±0.35) and increases in jump height (+10.1±2.7%; ES = 0.93±0.09). The number of weeks needed to reach the optimal F-v profile (12.6 ± 4.6) was correlated to the magnitude of initial FVimb (r = 0.82, p<0.01) for all participants regardless of their initial subgroup. No significant change in mechanical variables or jump performance was observed over the 3-week de-training period.

CONCLUSIONS

Collectively, these results provide useful insights into a more specific, individualized (i.e. based on the type and magnitude of FVimb) and accurate training prescription for jumping performance. Considering both training content and training duration together with FVimb may enable more individualized, specific and effective training monitoring and periodization.

The Effect of the Stretch-Shortening Cycle in the Force-Velocity Relationship and Its Association With Physical Function in Older Adults With COPD

This study aimed to evaluate the effect of the stretch-shortening cycle (SSC) on different portions of the force–velocity (F–V) relationship in older adults with and without chronic obstructive pulmonary disease (COPD), and to assess its association with physical function. The participants were 26 older adults with COPD (79 ± 7 years old; FEV₁ = 53 ± 36% of predicted) and 10 physically active non-COPD (77 ± 4 years old) older adults. The F–V relationship was evaluated in the leg press exercise during a purely concentric muscle action and compared with that following an eccentric muscle action at 10% intervals of maximal unloaded shortening velocity (V₀). Vastus lateralis (VL) muscle thickness, pennation angle (PA), and fascicle length (FL) were assessed by ultrasound. Habitual gait speed was measured over a 4-m distance. COPD subjects exhibited lower physical function and concentric maximal muscle power (P_max) values compared with the non-COPD group (both p < 0.05). The SSC increased force and power values among COPD participants at 0–100 and 1–100% of V₀, respectively, while the same was observed among non-COPD participants only at 40–90 and 30–90% of V₀, respectively (all p < 0.05). The SSC induced greater improvements in force, but not power, among COPD compared with non-COPD subjects between 50 and 70% of V₀ (all p < 0.05). Thus, between-group differences in muscle power were not statistically significant after the inclusion of the SSC (p > 0.05). The SSC-induced potentiation at 50–100% of V₀ was negatively associated with physical function (r = -0.40–0.50), while that observed at 80–100% of V₀ was negatively associated with VL muscle thickness and PA (r = -0.43–0.52) (all p < 0.05). In conclusion, older adults with COPD showed a higher SSC-induced potentiation compared with non-COPD subjects, which eliminated between-group differences in muscle power when performing SSC muscle actions. The SSC-induced potentiation was associated with lower physical function, VL muscle thickness, and VL PA values. The SSC-induced potentiation may help as a compensatory mechanism in those older subjects with a decreased ability to produce force/power during purely concentric muscle actions.

Optimisation of applied loads when using the two-point method for assessing the force-velocity relationship during vertical jumps

This study aimed to compare the reliability and validity of the force-velocity (F-V) relationship parameters obtained from two-point methods differing in the distance between experimental points, and to evaluate the acute change in unloaded jump height after a vertical jump testing procedure based on multiple loads. Totally, 18 men randomly performed two sessions of the squat jump (SJ) and two sessions of the countermovement jump (CMJ) exercises against five external loads (17, 30, 45, 60 and 75 kg). The unloaded jump height was evaluated before and after each testing procedure. Five two-point methods (0-17, 0-30, 0-45, 0-60 and 0-75 kg) and the multiple-point method (0-17-30-45-60-75 kg) were used to model the F-V relationship. The most distant two-point method (0-75 kg) revealed a comparable reliability (CV< 12.1%; ICC> 0.72) and high concurrent validity (r > 0.91) with respect to the multiple-point method (CV< 10.9%; ICC> 0.72). The reliability and validity of the two-point methods decreased with the proximity of the applied loads. Unloaded jump height was significantly reduced after both testing procedures (p < 0.05). These results support the two-point method based on distant loads as a quick and less prone to fatigue procedure for testing the F-V relationship through vertical jumps.

Relationship between vertical and horizontal force-velocity-power profiles in various sports and levels of practice

This study aimed (i) to explore the relationship between vertical (jumping) and horizontal (sprinting) force–velocity–power (FVP) mechanical profiles in a large range of sports and levels of practice, and (ii) to provide a large database to serve as a reference of the FVP profile for all sports and levels tested. A total of 553 participants (333 men, 220 women) from 14 sport disciplines and all levels of practice participated in this study. Participants performed squat jumps (SJ) against multiple external loads (vertical) and linear 30–40 m sprints (horizontal). The vertical and horizontal FVP profile (i.e., theoretical maximal values of force (F₀), velocity (v₀), and power (P_max)) as well as main performance variables (unloaded SJ height in jumping and 20-m sprint time) were measured. Correlations coefficient between the same mechanical variables obtained from the vertical and horizontal modalities ranged from −0.12 to 0.58 for F₀, −0.31 to 0.71 for v₀, −0.10 to 0.67 for P_max, and −0.92 to −0.23 for the performance variables (i.e, SJ height and sprint time). Overall, results showed a decrease in the magnitude of the correlations for higher-level athletes. The low correlations generally observed between jumping and sprinting mechanical outputs suggest that both tasks provide distinctive information regarding the FVP profile of lower-body muscles. Therefore, we recommend the assessment of the FVP profile both in jumping and sprinting to gain a deeper insight into the maximal mechanical capacities of lower-body muscles, especially at high and elite levels.

Methods of Power-Force-Velocity Profiling During Sprint Running: A Narrative Review

The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting. Stationary cycle ergometers have been the most common mode of assessment to date, followed by specialized treadmills used to profile the mechanical outputs of the limbs during sprint running. The most recent methods use complex multiple-force plate lengths in-ground to create a composite profile of over-ground sprint running kinetics across repeated sprints, and macroscopic inverse dynamic approaches to model mechanical variables during over-ground sprinting from simple time-distance measures during a single sprint. This review outlines these approaches chronologically, with particular emphasis on the computational theory developed and how this has shaped subsequent methodological approaches. Furthermore, training applications are presented, with emphasis on the theory underlying the assessment of optimal loading conditions for power production during resisted sprinting. Future implications for research, based on past and present methodological limitations, are also presented. It is our aim that this review will assist in the understanding of the convoluted literature surrounding mechanical sprint profiling, and consequently improve the implementation of such methods in future research and practice.

Two-Load Method for Distinguishing Between Muscle Force, Velocity, and Power-Producing Capacities

It is generally accepted that muscles may have different mechanical capacities, such as those for producing high force (F), velocity (V), and power (P) outputs. Nevertheless, standard procedures for evaluation of muscle function both in research and in routine testing are typically conducted under a single mechanical condition, such as a single external load. Therefore, the observed outcomes do not allow for distinguishing between the different muscle capacities. As a result, the outcomes of most routine testing procedures are of limited informational value, whereas a number of issues debated in research have originated from arbitrarily interpreted experimental findings regarding specific muscle capacities. A solution for this problem could be based on the approximately linear and exceptionally strong F-V relationship typically observed from various functional tasks performed under different external loads. These findings allow for the 'two-load method' proposed here: the functional movement tasks (e.g., maximum jumping, cycling, running, pushing, lifting, or throwing) should be tested against just two distinctive external loads. That is, the F-V relationship determined by two pairs of the F and V data could provide the parameters depicting the maximum F (i.e., the F-intercept), V (V-intercept), and P (calculated from the product of F and V) output of the tested muscles. Therefore, the proposed two-load method applied in both research and routine testing could provide a deeper insight into the mechanical properties and function of the tested muscles and resolve a number of issues debated in the literature.

Training at maximal power in resisted sprinting: Optimal load determination methodology and pilot results in team sport athletes

AIMS

In the current study we investigated the effects of resisted sprint training on sprinting performance and underlying mechanical parameters (force-velocity-power profile) based on two different training protocols: (i) loads that represented maximum power output (Lopt) and a 50% decrease in maximum unresisted sprinting velocity and (ii) lighter loads that represented a 10% decrease in maximum unresisted sprinting velocity, as drawn from previous research (L10).

METHODS

Soccer [n = 15 male] and rugby [n = 21; 9 male and 12 female] club-level athletes were individually assessed for horizontal force-velocity and load-velocity profiles using a battery of resisted sprints, sled or robotic resistance respectively. Athletes then performed a 12-session resisted (10 × 20-m; and pre- post-profiling) sprint training intervention following the L10 or Lopt protocol.

RESULTS

Both L10 and Lopt training protocols had minor effects on sprinting performance (average of -1.4 to -2.3% split-times respectively), and provided trivial, small and unclear changes in mechanical sprinting parameters. Unexpectedly, Lopt impacted velocity dominant variables to a greater degree than L10 (trivial benefit in maximum velocity; small increase in slope of the force-velocity relationship), while L10 improved force and power dominant metrics (trivial benefit in maximal power; small benefit in maximal effectiveness of ground force orientation).

CONCLUSIONS

Both resisted-sprint training protocols were likely to improve performance after a short training intervention in already sprint trained athletes. However, widely varied individualised results indicated that adaptations may be dependent on pre-training force-velocity characteristics.